Visually Meaningful Image Encryption Based On Discrete Quantum Random Walks

The development of science and technology makes the transmission of information more and more frequent and important.What accompanies this situation is the endless stream of information security issues.Information security includes many aspects and the security of image data is an important research branch.The traditional image encryption algorithms are designed to encrypt original images to noise-like or texture-like images.The security of the traditional image encryption algorithms mainly depends on the encryption algorithm and the key.The traditional image encryption algorithms protect the image information to a certain extent.However,the visual texture of the secret image makes it easy to be the target of the attack.Therefore,this paper will design visually meaningful image encryption algorithms.The cipher images encrypted by this paper's encryption algorithms have little difference with the normal images,so they can distract the attention of the attackers.This paper designs visually meaningful encryption algorithms based on discrete quantum random walk(DQRW),discrete wavelet transform and so on.The concrete contents of this paper are as follows:To begin with,a pseudo random number generator(PRNG)is designed based on the DQRW on the(2N+1)*(2N+1)graph.Quantum random walk(QRW)has a high degree of non-linear properties,so theoretically the key generator which is designed based on its infinite key space.In addition to this advantage,the QRW model can be used to create excellent quantum algorithms that will run much faster than their classical counterparts.Because of the excellent properties,such as quantum interference,quantum entanglement,particles can move in different directions simultaneously,which can make the walk show a more nonlinear dynamic behavior than classical random walk.Through the safety tests such as periodicity,statistical complexity,recurrence plot and randomness tests,we can see that this quantum-based PRNG is of excellent security that proves the superiority of the model as a key generator.Secondly,a visually meaningful gray image encryption(VMGIE)based on the designed PRNG is designed in this paper.This algorithm includes three phases.The first one is a key generator.The second one is a bidirectional diffusion pre-encryption algorithm based on the designed key generator.The encryption algorithm encrypts a plain image into a noise-like or texture-like image by changing the value of pixels and scrambling the location of image pixels.In this paper,the security of the pre-encryption algorithm is proved by key space analysis,histogram analysis,correlation analysis,information entropy analysis,key sensitivity analysis and random tests.The third one is the second step encryption algorithm which encrypts the noise-like image into a visually meaningful final-encrypted image.Using VMGIE to encrypt the image,it will have a very good visual performance.There is almost no visual difference between the original image and the final-encrypted image,so the attackers cannot quickly pick out the target from a large number of images.In this paper,the key security analysis,visual security analysis,cutting attack analysis and calculation time analysis have been done for the VMGIE.The experimental results show that the VMGIE has a very superior image security effect.At the end of this paper,a visually meaningful color image encryption(VMCIE)algorithm is designed.And the histogram analysis,correlation analysis,key sensitivity analysis,visual security analysis and cutting attack analysis have been done for this algorithm.The experimental results conclude the security of VMCIE.